The present invention relates to a resist material for use in fabrication process or the like for semiconductor devices and a pattern formation method using the same.
In accordance with the increased degree of integration of semiconductor integrated circuits and downsizing of semiconductor devices, there are increasing demands for further rapid development of lithography technique. Currently, pattern formation is carried out through photolithography using exposing light of a mercury lamp, KrF excimer laser, ArF excimer laser or the like.
Recently, attempts have been made to apply immersion lithography to an ArF light source. Under these circumstances, it is regarded significant to increase the life of the lithography using the ArF excimer laser, and resist materials for use of the ArF excimer laser are now being developed. Some of such ArF resists may include a lactone ring in the composition of the polymer (for example, see T. Kudo et al., “Illumination, Acid Diffusion and Process Optimization Considerations for 193 nm Contact Hole Resists”, Proc. SPIE, vol. 4690, p. 150 (2002)). This is because a lactone ring is expected to exhibit a function to improve the adhesive property between a resist pattern and a target film.
Now, a pattern formation method using a conventional ArF resist will be described with reference to FIGS. 5A through 5D.
First, a positive chemically amplified resist material including lactone in its base polymer and having the following composition is prepared:
Base polymer: poly(2-methyl-2-adamantyl2gmethacrylate (50 mol %) - γ-butyrolactonemethacrylate (40 mol %) - 2-hydroxyadmantylmethacrylate (10 mol %))Acid generator: triphenylsulfonium trifluoromethane sulfonate0.06gQuencher: triethanolamine0.002gSolvent: propylene glycol monomethyl ether acetate20g
Next, as shown in FIG. 5A, the chemically amplified resist material is applied on a substrate 1, so as to form a resist film 2 with a thickness of 0.35 μm.
Then, as shown in FIG. 5B, the resist film 2 is subjected to pattern exposure by irradiating with exposing light 3 of ArF excimer laser with NA (numerical aperture) of 0.68 through a mask 4.
After the pattern exposure, as shown in FIG. 5C, the resist film 2 is baked at a temperature of 105° C. for 60 seconds. Thereafter, the resultant resist film 2 is developed with a 0.26 N tetramethylammonium hydroxide developer. Thus, as shown in FIG. 5D, a resist pattern 2a with a line width of 0.09 μm made of an unexposed portion of the resist film 2 is obtained.
As shown in FIG. 5D, however, the resist pattern 2a obtained by the pattern formation method using the conventional ArF resist is in a defective shape.